Mattress



FIG. 1 is a top perspective view of a mattress;

FIG. 2 is a first transverse side view of the mattress of FIG. 1;

FIG. 3 is a second transverse side view of the mattress of FIG. 1;

FIG. 4 is a first longitudinal side view of the mattress of FIG. 1;

FIG. 5 is a second longitudinal side view of the mattress of FIG. 1;

FIG. 6 is a top view of the mattress of FIG. 1; and,

FIG. 7 is a bottom view of the mattress of FIG. 1.

Broken lines in the drawings depict features that form no part of the claimed design. 

CLAIM The ornamental design for a mattress, as shown and described. 